新增表字段，并赋有意义的值

ALTER TABLE b_contract ADD COLUMN pay_company_name VARCHAR(255) DEFAULT NULL COMMENT 'xxx' AFTER pay_company;

UPDATE b_contract c
SET c.pay_company_name = (
    SELECT
        o.full_name
    FROM
        crm_business_opportunity AS o
    WHERE
        o.id = c.pay_company
);